Animal Behavior

Behavioral Ecology

Why do animals pretend to be hurt?

Pufferfish are any of a number of species found in warm seas that use a special adaptation of the gullet to inflate their bodies to nearly twice the normal size. Pufferfish, blowfish, and similar animals do this in response to a perceived threat. The increased size and unpalatable-looking spines make the potential prey look quite unappetizing to predators. One of these fish, the Fugu rubripes, or the Japanese pufferfish, is a specialty in sushi restaurants—but only specially trained chefs can safely prepare the fish for consumption by minimizing the presence of the fish’s deadly toxin, called tetrodotoxin, a compound 1,000 times deadlier than cyanide.

Among bird watchers, the female killdeer is well known for pretending to be hurt, especially when a potential predator appears within the vicinity of her nest. In an act worthy of the human stage, the killdeer will adopt a posture of wing-dragging, making it appear that she is injured and an easy catch. The female will gradually lead the predator away from her nest—usually filled with eggs or hatchlings—eventually flying off when the predator is at a safe distance from the nest. Another pretender is the common or Virginia opossum (Didelphis virginiana)—the only marsupial in the southern and eastern United States. When threatened or frightened, the opossum will lie quite still, with stiffened limbs and a fixed gaze, appearing as if dead. When the perceived threat is over, the opossum will return to its normal, nocturnal activities.